1. Field of the Invention
The present invention relates to a method for registering wireless terminal to a communication system and in particular to a method for securely registering a wireless LAN (WLAN).
2. Description of the Related Art
In U.S. patent application Pub No: 2002/0009199 and in “Wireless LAN Access network architecture for mobile operators” IEEE communication magazine Vol 39, No 11 pp. 82˜89, November 2001, a method and a system is disclosed for obtaining a ciphering key via a wireless local area network (WLAN). The obtained ciphering key is applied to encrypt data transmitted between WLANs and wireless terminals. As shown in FIG. 1, GPRS network 100 comprises a base transceiver station (BTS)114, a radio access network (RAN) 104, a serving GPRS support node (SGSN) 106, a GPRS gateway support node (GGSN), a mobile switch center with a home location register (MSC/HLR) 110, and a GPRS billing gateway 112. Each of the above is connected via a cell mobile network 116. The wireless terminal 20, comprising a WLAN adapter and a SIM card, is capable of registering the GPRS network by the SIM card.
The wireless terminal 20 can register a WLAN network by a user ID stored in the wireless terminal 20. The user ID may be predetermined corresponding to the SIM card. The user ID transferred from either access point 202a or 202b is delivered to access control device 204. The access control device 204 manages the registration processes of the wireless terminals and filters out the packets from unauthorized wireless terminals. The access control device 204 also delivers the user ID by internet protocol (IP) network 22 to the authentication server 206 (step S102). The authentication server 206 requests the authentication information of the wireless terminal 20 from remote mobile switching center or home location register (MSC/HLR) (step S103). The access control device 204 obtained authentication information from the authentication server 206 then manages the register request from the wireless terminal 20.
Because the international mobile subscriber identity (IMSI) information is needed for the registration process to MCS/HLR 110, the packets including IMSI of the wireless terminal 20 delivered from access points 20a or 20b pass through the IP network 22 to reach MCS/HLR 110. When the wireless terminal 20 moving forward and backward between the access points, it will cause duplicate login to MCS/HLR 110 and caused decreasing the performance of the network and increasing delay of end-to-end communication between mobile stations or (MS-to-MS). Also, unencrypted packets comprising IMSI are delivered via an open network, such as an IP network. The unsecured data transmission over the network exposes entire system to threats, such as data theft.
The 3GPP protocol combines the global systems of mobile (GSM) network, the general packet radio service (GPRS) and the universal mobile telecommunication system (UMTS) in an attempt to provide a well-developed architecture for protecting the IMSI in wireless communication. For example, only the temporary mobile station number (TMSI) or packet temporary mobile station number (P-TMSI) is delivered during transmission. The relationship between IMSI and P-TMSI or TMSI is stored in a visited location register (VLR) of SSGN, and the information updates periodically.